As has been described above, chitin deacetylase is an enzyme hydrolyzing the N-acetyl groups in chitin, chitin oligosaccharide, and other compounds containing N-acetylated aminosugar residues.
As described above, the usefulness of chitosan, which is a deacetylated product of chitin, is approved in a wide variety of fields. In the food field alone, the usefulness thereof is illustrated by for example thickening action, cholesterol decreasing action, hypotensive action, prophylactic effect against gout and hyperurinacidemia, prophylactic effect against osteoporosis, promotion of the growth of Bifidus bacteria, suppression of the growth of E. coli and Clostridium perfringens, antitumor activity and the like.
Conventionally, the N-acetyl group in sugar residues has been hydrolyzed, primarily by chemical hydrolysis with alkalis. It has been remarked that the method is disadvantageous due to the occurrence of side reactions and the difficulty in the control of the reaction and the generation of alkaline liquid waste.
As a means for overcoming the disadvantages, energetic research works have been carried out over an enzymatic deacetylation method under mild conditions, by using chitin deacetylase. Specifically, attention has been focused on a chitin deacetylase derived from Deuteromycotina (imperfect fungi) (Japanese Patent Kokai Hei 8-289785).
The chitin deacetylase derived from an imperfect fungi is advantageous in that the enzymatic reaction is hardly inhibited by a reaction product, acetic acid and in that low molecular chitin oligosaccharides etc. can also be deacetylated. Therefore, the deacetylase is very suitable for industrial use. Furthermore, the enzyme has a wide range of activities such as activity to eliminate the N-acetyl group in the N-acetylated aminosugar residues other than those in chitin, so the enzyme can be applied to the synthesis of novel sugar chains.
The imperfect fungi having been researched most energetically as bacteria to obtain a chitin deacetylase is Colletotrichum lindemuthianum.
Because Colletotrichum lindemuthianum is a plant pathogenic fungus, however, the handling thereof is so disadvantageously difficult in terms of safety. From the respect of production of the enzyme, additionally, said fungus is disadvantageous in that a longer time is needed for the enzyme to be secreted in a fungal culture broth, but the enzyme to be recovered is a little.